1. Field of the Invention
This invention relates to a chisel-holder changing system for a road milling machine, a coal cutting machine, or the like, to which a chisel holder is fastened in an exchangeable manner by a connecting mechanism, wherein the chisel holder accommodates at least one chisel that can be exchanged, and wherein a central longitudinal axis of the chisel is set at a working angle of less than 90xc2x0 relative to the surface to be worked.
2. Description of Related Art
A chisel-holder changing system is known from German Patent Reference DE 43 22 401 C2. The chisel-holder changing system features a base part that is welded onto a surface of a roller body that projects outwardly. The base part has a plug receiver, in which a plug connector of the chisel holder can be inserted. The chisel holder has a receiving hole, in which the chisel shaft of a circular-shaft chisel is inserted. The chisel holder can be fixed to the base part using a fastening screw. In the assembled state, the central longitudinal axis, the axis of rotation, of the circular-shaft chisel is slanted with respect to the surface to be worked.
One object of this invention is to provide a chisel-holder changing system of the initially mentioned type, with which different removal results can be obtained with regard to the quality of the worked surface.
This object is achieved with a chisel holder that can be fixed in two or more attachment positions to a base part, and a central longitudinal axis of the chisel is slanted at different working angles in the various attachment positions.
Due to different settings of the chisel, a single chisel-holder changing system can realize different removal results. For example, for road milling, through variation of the working angle, either coarse or fine milling can be produced.
According to one preferred embodiment of this invention, the chisel holder is supported by a support surface on a contact surface of the base part, and for implementing the different attachment positions, the chisel holder can be moved on its support surface relative to the contact surface.
In order to be able to change the chisel position quickly, it is possible to adjust the chisel holder stepwise relative to the base part. In particular, the individual steps correspond to determined, preferred working angles. For road milling, these angles are, for example, 35xc2x0, 40xc2x0, and 45xc2x0.
The step-wise adjustment can be implemented, for example, such that the chisel holder has toothing that engages counter-toothing of the base part, and such that the toothing and the counter-toothing have flat support edges that extend perpendicular to the movement direction of the chisel holder relative to the base part. With the support edges, the forces occurring during operation can be reliably transferred into the base part.
Normally, the chisel-holder changing system is mounted on a roller-shaped base that can move about an axis of rotation. So that the forces acting in the direction of the axis of rotation can also be reliably received in the working insert, a chisel-holder changing system according to this invention has the counter-toothing of the base part with two sets of partial toothing. The sets of partial toothing are slanted for receiving transverse forces in the direction perpendicular to the direction of advance of the chisel.
An alternative embodiment of the chisel-holder changing system can be implemented, for example, so that the base part has a contact part that is configured with a plurality of concentrically arranged tooth elements of the counter-toothing. The chisel holder carries a gripping plate that has toothing adapted to the counter-toothing, and the chisel holder can rotate relative to the base part about an adjustment axis that is perpendicular to the direction of advance of the chisel. Such a connecting mechanism can also be configured as Hirth-type serrations. Due to the plurality of tooth elements, extremely high forces can be transmitted by this connecting mechanism.
In order to create a fixed connection of the chisel holder to the base part, which simultaneously allows simple and quick changing of the working angle, in one embodiment of this invention the chisel holder has a base carrying a holder attachment for receiving the chisel. The base features an oblong hole that is aligned with a threading receiver of the base part. A fastening screw can be inserted into the oblong hole and the screw can be screwed into the threading receiver, and the chisel holder can be adjusted when the fastening screw is removed.
A screw head of the fastening screw can be housed for protection in a recess that expands and connects to the oblong hole.
An especially good and quick attachment of the screw head to the chisel holder can be achieved if the screw head is designed as an oval-head screw head.
Wear or excessive stress can damage a chisel holder. In order to prevent the chisel holder from breaking uncontrollably and damaging the base part, the chisel holder carries a holder attachment on a base. The holder attachment has a receiving hole for the chisel stem, and the holder attachment is connected to the base through a set breaking point.